Process of manufacturing leather and product used in connection therewith



Patented Oct. 2, 1934 PROCESS F MANUFACTURING LEATHER AN-E) PRODUCT USED' IN CONNECTION QharlesGLShaW, Huntsville, Ontario, and Jacques Hoffman, Toronto, Ontario, Canada No Drawing; Application June'- 3', 1930, Serial No. 459,104. in Canada No'vemberZB, 1929..

I leather after the filling and tanning steps. Previous to our discoveries in connection with the application of' coating materials, the adhesion of such materials to the' grainof sole leather 'was' such; that when the leather was subjected to such operations as drumming with fillers in a stufiing after having been coated, the coating would-not adhere andwould be mutilated and destroyed by such operations. Furthermore, when leather, which had previously been filled with such materials as wax, resin, oil,- tanning extract, sugar and the like, was coated or painted for the purpose of rectifying the unpleasant color caused bythe-filling, any coating so applied would be removed by subsequent operations in the shoe, factory, thus exposing the unpleasant color beneath. j

In the application of permanent waterproof coatings on sole leather and particularly with reference to the adhesion of these coatings, there 80 are two principal controlling factors addition to the composition of the coating material itself; During our experimental work, the repeated failures. of the coatings-to adherewere at first. attributed to the tanning materials and 85 fillers lying upon the surface of the leather. 'Ifhese materials and fillers were almost-entirely of a water soluble nature and their presence was considered responsible for the failure of the adhesion when the coated leather was re -soaked.

4.0 A great many tests were carried out in applying coatings to leather-from which the fillers had been carefully cleansed from the surface. 'Those tests proved that neither the quantity of filler 'nor the composition of' the filler had much eifect upon the adhesion of the coating. We then discovered that the physical properties of the surface or the leather ordinarilyconstituted the controlling factor in the adhesion of a coating material to sole leather which was reasonably free from an excess offillers. Coatings for sole leather were made adherent by applying the coating to the leather; in the'absence of the glossing; effect of the setting out and' finishing operations, which latter operations had a tend-- ency to compact the surface 'or -hyaline layer of the leather and form'of it a filter into which the constituents of the coating material would not penetrate. We then found that if the sole leather was previously completely saturated with I so fillers such as wax, grease or water-soluble fillers,

the adhesion would then be controlled by the quantity and the nature of the filling ingredients.

We have now discoveredv that coating materials may be applied to leather before the completion of the filling process and even insome cases before the completion of the tanning operations. In fact, the coating materials may be appliedand the leather may be subsequently saturated, or filled as desired, with any suitable material, and with the coating applied so as to adhere properly to the leather fibre or substance itself, the subsequent filling operation having no effect upon the "adhesion.

One of the principal objects. of this invention is to incorporate intothe leather an extraordinary amount of tanning and/or filling materialsv without interfering with the adhesion of a coating material applied for the purpose of rectifying the color of the-leather so produced.

Another object is to eliminate the cost of refinishing the soles after the shoes have been made.

A further object is .to provide a product in which the applied coatings may be both oil proof and water-proof, but which product will neverthelessv permit the rapid soaking of the leather through the coating.

A still further object is to provide a product which will enable the manufacturer of sole leather to disregard color in the selection of his tanning and filling materials and also the extent to which many fillers may be incorporated without making the leather unsightly.

Our invention consists essentially in the process. of applying one or more coating compositions, either-clear or pigmented, tothe grain surface of sole leather prior to the completion of the filling operation, or even prior to the completion of the tanning operation. When filling materials such as corn sugar, tanning extract, oil, wax, resin, asphalt,um,and the like, are incorporated into the leather in large quantities, prior to the coating process, the adhesion of the coating to the leather is. seriously interfered with as the bonding,'in such, cases,-,is more apt to be to the filling substance rather than to the leather substance.

In carrying out our invention, the following procedure maybe employed. The leather is taken fromthe tan liquor and preferably washed to remove water-soluble substances from the-surface of the leather. It is then dried so as not to exceed about forty percent moisture by'weight. It may be stated that the moisture content is determinedby the constituents of, the coating composition, but, generally speaking; the leather shouldv be dried. to a point Where proper adhesion of the first coating takes place easily. The leather is now ready for the coating compositions which are preferably applied by means of an air spray gun. The composition of the priming coat contate 3 parts, toluol 20 parts, and castor oil 6' parts. This finishing coat'is allowed to dry and jthe leather may then be' saturated and fil1ed by drumming in a mixture such as the following:

, Parts Corn sugar e 20 Water; l0 Magnesium sulphate; 10 Stearine 20 Parafiine wax 20 Asphalt n 15 Varnolene a petroleum distillate used as a turpentine substitute having a boiling range, from about 310 to 415"- 15 Sulphonated fish oil 5 This drumming operation is preferably carried out at a temperature between 100. F. and 130 F. The surface of the leather is then freed of excess filling composition by a.setting outoperation on the grain side and at the same time spraying the grain surface of the'leather with water warmed to not over 100 F. for vegetable tanned leather and not over 200 F. for chrome tanned leather.

The coating on the grain surface is then sponged with a substance suchas naphtha to remove the filling material from the surface. An additional. coating of a finishing composition similar to that mentioned ,above is then applied as before and the leather is afterwards thoroughly dried and compacted in the ordinary manner of treating s ole leather. 1 W

While weprefer to perform the filling opera tion in the manner abovedescribed, the filling materials may be incorporated into the leather by a process'of immersion or'by treating thefleather in a vacuum in the presence of the fillers or by subjecting the leather which is submerged in the fillers to pressure within a suitable vessel; It should be observed that the coating will, not adhere satisfactorily to the leather if, in drying from the tan liquors, it becomes excessively oxidized or liquorl-stainedfi, or if excessive amounts of water or water-soluble substances are present.

While we have-found it preferable to use a priming coat and a finishing coat consistingof the ingredients infthe proportions above stated, we do not restrict ourselves to such proportions and we desire to include Within the scope of our invention equivalent ingredients as modifications thereof. We do, however, find it essential that the coating compositions should contain either a cellulose ester or a resin,'preferably a synthetic resin. The compositions may, if desired, contain suitable pigments or coloring matter.

These coriipositioris should preferably be applied by means of an air spray gun so as to prevent permanent plugging of'the hair holes in the leather, thus facilitating the rapid penetration of tanning agents or liquid matter into the pores or hair holes of the leather; 'sitions may be applied in any manner as by pour- 1very flexible by impregnation with gums; chrome leather, which maybe given the appearthrough these hair holes into the leather and this However, the compoing or-swabbing, in which-case thehair holes should be re-opened by;mechani1cal working of the leather. The process is intended to be applied to, sole leather which has not been completely filled and which may be partially or completely tanned. After the application of the first coat, the leather may be filled with any suitable filling material, excepting those fillers which exert a softening or solvent action upon the coating. Any stains consequent upon the filling of the'leather may be covered over by the application of a further coat of finishing compound conadhesion of the coating materials is more to the actual leather fibres and less to the filling or tanning materials. E. 1

By means of this. invention, a product may be produced having a'uniform coating of any desired color regardless of the type of tanning or fillingmaterial employed. Such leather is particularly suitable for loggers boots, whichmay be made impervious to water; to Goodyear insoles, which may be made exceedingly tough-by stuffing. with wax or the like so that they .will not stain hosiery; to sport shoes, which may be made to (no ance of oak tanned leather; and to many other types of leather useful for various purposes.

" By this process a perfect adhesion ofthe coating to the leather is produced, so that it will with- 5 'stand the action of subsequent drum stufiing,.or other filling processes, and will not be damaged terial to nourish and preserve theleather fibre without producing unsightly colors or stains. Finally,.as a result of our process, a'very rapid penetration of the fillers through the coating takesf'place because when the hair holes are open and unclogged, the fillers or tanning liquors pass is a great advantagein a leather manufacturing process. Although ,this' process has been described as being applied particularly to sole leather, it may be applied to other types of leather. Having thus described our invention, what' we claim is: A process of manufacturing sole leather which includes the steps of applying one or more permanently adhesive waterproof coatings, containing such a material, as cellulose ester, to the surface of sole leather prior to the ,completion of the filling operation, rupturing the coating materials bridged over the hair holes of the leather and then subjectingthe leather to the filling finishing operations.

i 7 Cruise. SHAW.

JACQUES HOFFMAN.

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